Is there a way to view images in Render View with gray background? Is there a shader that I can put say on a grid to serve as that? I'm rendering images with some black info and I couldn't see it because the BG is black. Thank you.

You can use a custom image in the camera node.

You can change the background color in the display options (hotkey ‘d’) and then turn on Transparency (Shift+Ctrl+T) to factor in the A channel.